Cryogenic needle with freeze zone regulation

ABSTRACT

A cryogenic needle of a cryogenic system is coupled to a heater. While the needle is inserted into target tissue beneath skin, the heater provides heat to protect the skin. Power supplied to the heater is used to interpolate performance of the needle and/or operating parameters of the cryogenic system.

CROSS REFERENCE TO RELATED APPLICATION DATA

The present application is a Continuation of U.S. Ser. No. 15/065,685filed Mar. 9, 2016 (now U.S. Pat. No. 10,213,244); which is a Divisionalof U.S. Ser. No. 13/741,360 filed Jan. 14, 2013 (now U.S. Pat. No.9,314,290); which claims the benefit of U.S. Provisional Appln. No.61/586,694 filed Jan. 13, 2012; the full disclosures which areincorporated herein by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

The present invention is generally directed to medical devices, systems,and methods, particularly for cooling-induced remodeling of tissues.Embodiments of the invention include devices, systems, and methods forapplying cryogenic cooling to dermatological tissues so as toselectively remodel one or more target tissues along and/or below anexposed surface of the skin. Embodiments may be employed for a varietyof cosmetic conditions, optionally by inhibiting undesirable and/orunsightly effects on the skin (such as lines, wrinkles, or cellulitedimples) or on other surrounding tissue. Other embodiments may find usefor a wide range of medical indications. The remodeling of the targettissue may achieve a desired change in its behavior or composition.

The desire to reshape various features of the human body to eithercorrect a deformity or merely to enhance one's appearance is common.This is evidenced by the growing volume of cosmetic surgery proceduresthat are performed annually.

Many procedures are intended to change the surface appearance of theskin by reducing lines and wrinkles. Some of these procedures involveinjecting fillers or stimulating collagen production. More recently,pharmacologically based therapies for wrinkle alleviation and othercosmetic applications have gained in popularity.

Botulinum toxin type A (BOTOX®) is an example of a pharmacologicallybased therapy used for cosmetic applications. It is typically injectedinto the facial muscles to block muscle contraction, resulting intemporary enervation or paralysis of the muscle. Once the muscle isdisabled, the movement contributing to the formation of the undesirablewrinkle is temporarily eliminated. Another example of pharmaceuticalcosmetic treatment is mesotherapy, where a cocktail of homeopathicmedication, vitamins, and/or drugs approved for other indications isinjected into the skin to deliver healing or corrective treatment to aspecific area of the body. Various cocktails are intended to effect bodysculpting and cellulite reduction by dissolving adipose tissue, or skinresurfacing via collagen enhancement. Development ofnon-pharmacologically based cosmetic treatments also continues. Forexample, endermology is a mechanical based therapy that utilizes vacuumsuction to stretch or loosen fibrous connective tissues which areimplicated in the dimpled appearance of cellulite.

While BOTOX® and/or mesotherapies may temporarily reduce lines andwrinkles, reduce fat, or provide other cosmetic benefits they are notwithout their drawbacks, particularly the dangers associated withinjection of a known toxic substance into a patient, the potentialdangers of injecting unknown and/or untested cocktails, and the like.Additionally, while the effects of endermology are not known to bepotentially dangerous, they are brief and only mildly effective.

In light of the above, improved medical devices, systems, and methodsutilizing a cryogenic approach to treating the tissue have beenproposed, particularly for treatment of wrinkles, fat, cellulite, andother cosmetic defects. These new techniques can provide an alternativevisual appearance improvement mechanism which may replace and/orcompliment known bioactive and other cosmetic therapies, ideallyallowing patients to decrease or eliminate the injection of toxins andharmful cocktails while providing similar or improved cosmetic results.These new techniques are also promising because they may be performedpercutaneously using only local or no anesthetic with minimal or nocutting of the skin, no need for suturing or other closure methods, noextensive bandaging, and limited or no bruising or other factorscontributing to extended recovery or patient “down time.” Additionally,cryogenic treatments are also desirable since they may be used in thetreatment of other cosmetic and/or dermatological conditions (andpotentially other target tissues), particularly where the treatments maybe provided with greater accuracy and control, less collateral tissueinjury and/or pain, and greater ease of use.

While these new cryogenic treatments are promising, careful control oftemperature along the cryogenic probe is necessary in order to obtaindesired results in the target treatment area as well as to avoidunwanted tissue injury in adjacent areas. Once the probe is introducedinto a target treatment area, cooling fluid flows through the probe andprobe temperature decreases proximally along the length of the probetoward the probe hub. Ideally, temperature at the probe is known duringtreatment, however, sensing devices cannot typically be placed withinsmall probes, due to size constraints. Therefore, it would be desirableto provide a cryogenic device that helps control needle temperaturedespite having a sensorless probe.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention provide improved medical devices, systems,and methods. Many of the devices and systems described herein will bebeneficial for monitoring operational parameters when cryogenicallyremodeling target tissue.

One embodiment of the invention relates to a method for cryogenicallytreating tissue. In the method a needle probe having at least one needlewith a distal portion and a proximal portion can be provided. The needleprobe can be coupled to a coolant supply system regulated by a valve.The at least one needle can be advanced into target tissue. A valve canbe regulated to provide the at least one needle probe with coolant toform an cooling zone in the target tissue. Power can be provided to aheater assembly of the needle probe to protect non-target tissue. Atleast one characteristic of the heater can be monitored while providingpower to the heater. Coolant can be metered to the needle probe usingthe valve based on a correlation of the monitored characteristic of theheater, such that the cooling zone is substantially maintained within anallowable size tolerance.

In one aspect of the method, at least one monitored characteristic canbe temperature or other spatial gradient of the heater assembly.

In another aspect of the method, at least one monitored characteristiccan be power supplied to the heater assembly.

In another aspect of the method, metering the coolant includesregulating the valve to halt or decrease coolant flowing in the needleprobe long enough for the cooling zone to decrease in size within theallowable size tolerance.

In another aspect of the method, metering the coolant includesregulating the valve to provide or increase coolant flowing in theneedle probe long enough for the cooling zone to increase in size withinthe allowable size tolerance.

In another aspect of the method, the allowable size tolerance isdetermined by performing a tissue pre-characterization routine using theneedle probe.

In another aspect of the method, regulating the valve is based on apredetermined treatment algorithm.

In another aspect of the method, the at least one characteristic of theheater includes at least one of a heater power, heat transfer rate, heatflux, temperature change rate, and temperature differential.

Another embodiment of the invention relates to another method forcryogenically treating tissue. In the method, coolant can be regulatedto a needle probe using a valve. The needle probe can have at least oneneedle and a heater thermally coupled to the at least one needle. Powercan be provided to the heater based on power demand from the heater. Thepower supplied to the heater can be monitored. The monitored power canbe correlated with at least one of a tissue characteristic and operatingparameter.

In one aspect of the method, the valve can be actuated to provide moreor less coolant to the needle probe based on at least one of thecorrelated tissue characteristic and operating parameter.

In another aspect of the method, power demand is based on maintainingthe heater at a particular temperature.

In another aspect of the method, the heater includes a thermallyconductive element, with the thermally conductive element beingthermally coupled to a proximal skin engaging portion of the needle.

In another aspect of the method, temperature of a thermally conductiveelement coupled to the heater can be monitored.

In another aspect of the method, the at least one needle can include asensorless needle.

In another aspect of the method, the at least one sensorless needle canbe 25 gauge or smaller.

In another aspect of the method, a user indication can be provided basedon the correlation.

In another aspect of the method, the user indication relates to a tissuetype.

In another aspect of the method, the user indication relates to needleprobe status.

In another aspect of the method, regulating cooling includes operatingthe valve to provide coolant to the needle probe for a predeterminedperiod of time.

In another aspect of the method, the monitored power can be correlatedwith an operating parameter indicating malfunction of the valve.

In another aspect of the method, a user alert can be provided based onthe malfunction of the valve.

In another aspect of the method, the tissue characteristic comprisestissue type or depth of insertion.

In another aspect of the method, the at least one operating parametercomprises at least one of heat transfer rate, heat flux, temperaturechange rate, and temperature differential.

Another embodiment of the invention relates to a system including acontroller. A cooling supply system having a valve can be controlled bythe controller. A needle probe can be coupled to the controller andconfigured to receive coolant from the coolant supply system. The needleprobe can have at least one needle and a heater thermally coupled to theat least one needle. The controller can be configured to regulatecoolant to the needle probe using the valve, provide power to the heaterbased on power demand from the heater, monitor power supplied to theheater, and correlate the monitored power with at least one of a tissuecharacteristic and operating parameter.

In one aspect of the system, the heater can be further configured toactuate the valve to provide more or less coolant to the needle probebased on at least one of the correlated tissue characteristic andoperating parameter.

In another aspect of the system, power demand of the heater can be basedon maintaining the heater at a particular temperature.

In another aspect of the system, the heater can be thermally coupled toa thermally conductive element, with the thermally conductive elementbeing thermally coupled to a proximal skin engaging portion of theneedle.

In another aspect of the system, the controller can be furtherconfigured to monitor temperature of a thermally conductive elementcoupled to the heater.

In another aspect of the system, the at least one cryogenic needle canbe included least one cryogenic sensorless needle.

In another aspect of the system, the at least one sensorless needle is25 gauge or smaller.

In another aspect of the system, the controller can be furtherconfigured to provide a user indication based on the correlation. Basedon the tissue present, at least one operating parameter may change toaffect a particular treatment.

In another aspect of the system, the user indication relates to a tissuetype.

In another aspect of the system, the user indication relates to needleprobe status.

In another aspect of the system, the user indication relates toplacement of the needle probe in tissue

In another aspect of the system, the controller can be configured toregulate cooling by operating the valve to provide coolant to the needleprobe for a predetermined period of time.

In another aspect of the system, the at least one power characteristiccan be correlated to an operating parameter indicating malfunction ofthe valve.

In another aspect of the system, the controller can be configured toprovide a user alert based on the malfunction.

In another aspect of the method, the tissue characteristic comprisestissue type or depth of insertion.

In another aspect of the method, the at least one operating parametercomprises at least one of heat transfer rate, heat flux, temperaturechange rate, and temperature differential.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a self-contained subdermal cryogenicremodeling probe and system, according to an embodiment of theinvention.

FIG. 1B is a partially transparent perspective view of theself-contained probe of FIG. 1A, showing internal components of thecryogenic remodeling system and schematically illustrating replacementtreatment needles for use with the disposable probe.

FIG. 2 schematically illustrates components that may be included in thetreatment system.

FIGS. 3A-3B illustrate an exemplary embodiment of a clad needle probe,according to an embodiment of the invention.

FIG. 4 is a flow chart illustrating an exemplary algorithm for heatingthe needle probe of FIG. 3A, according to an embodiment of theinvention.

FIG. 5 is a flow chart schematically illustrating a method for treatmentusing the disposable cryogenic probe and system of FIGS. 1A and 1B,according to an embodiment of the invention.

FIG. 6A is a flow chart schematically illustrating a method fortreatment using the disposable cryogenic probe and system of FIGS. 1Aand 1B, according to an embodiment of the invention.

FIG. 6B is a flow chart schematically illustrating a method fortreatment using the disposable cryogenic probe and system of FIGS. 1Aand 1B, according to an embodiment of the invention.

FIG. 6C is a simplified depiction of the method of treatment of FIG. 6B.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides improved medical devices, systems, andmethods. Embodiments of the invention will facilitate remodeling oftarget tissues disposed at and below the skin, optionally to treat acosmetic defect, a lesion, a disease state, and/or so as to alter ashape of the overlying skin surface, while providing protection toportions of non-target tissues, including the skin, which are directlyabove the target tissues.

Among the most immediate applications of the present invention may bethe amelioration of lines and wrinkles, particularly by inhibitingmuscular contractions which are associated with these cosmetic defectsso as so improve an appearance of the patient. Rather than relyingentirely on a pharmacological toxin or the like to disable muscles so asto induce temporary paralysis, many embodiments of the invention will atleast in part employ cold to immobilize muscles. Advantageously, nerves,muscles, and associated tissues may be temporarily immobilized usingmoderately cold temperatures of 10° C. to −5° C. without permanentlydisabling the tissue structures. Using an approach similar to thatemployed for identifying structures associated with atrial fibrillation,a needle probe or other treatment device can be used to identify atarget tissue structure in a diagnostic mode with these moderatetemperatures, and the same probe (or a different probe) can also be usedto provide a longer term or permanent treatment, optionally by ablatingthe target tissue zone and/or inducing apoptosis at temperatures fromabout −5° C. to about −50° C. In some embodiments, apoptosis may beinduced using treatment temperatures from about −1° C. to about −15° C.,or from about −1° C. to about −19° C., optionally so as to provide apermanent treatment that limits or avoids inflammation and mobilizationof skeletal muscle satellite repair cells. In some embodiments,temporary axonotmesis or neurotmesis degeneration of a motor nerve isdesired, which may be induced using treatment temperatures from about−25° C. to about −90° C. Hence, the duration of the treatment efficacyof such subdermal cryogenic treatments may be selected and controlled,with colder temperatures, longer treatment times, and/or larger volumesor selected patterns of target tissue determining the longevity of thetreatment. Additional description of cryogenic cooling for treatment ofcosmetic and other defects may be found in commonly assigned U.S. Pat.No. 7,713,266 entitled “Subdermal Cryogenic Remodeling of Muscle,Nerves, Connective Tissue, and/or Adipose Tissue (Fat)”, U.S. Pat. No.7,850,683 entitled “Subdermal Cryogenic Remodeling of Muscles, Nerves,Connective Tissue, and/or Adipose Tissue (Fat)”, and U.S. patentapplication Ser. No. 13/325,004, entitled “Method for ReducingHyperdynamic Facial Wrinkles”, the full disclosures of which are eachincorporated by reference herein.

In addition to cosmetic treatments of lines, wrinkles, and the like,embodiments of the invention may also find applications for treatmentsof subdermal adipose tissues, benign, pre-malignant lesions, malignantlesions, acne and a wide range of other dermatological conditions(including dermatological conditions for which cryogenic treatments havebeen proposed and additional dermatological conditions), and the like.Embodiments of the invention may also find applications for alleviationof pain, including those associated with muscle spasms as disclosed incommonly assigned U.S. Pub. No. 2009/0248001 entitled “Pain ManagementUsing Cryogenic Remodeling” the full disclosure of which is incorporatedherein by reference.

Referring now to FIGS. 1A and 1B, a system for cryogenic remodeling herecomprises a self-contained probe handpiece generally having a proximalend 12 and a distal end 14. A handpiece body or housing 16 has a sizeand ergonomic shape suitable for being grasped and supported in asurgeon's hand or other system operator. As can be seen most clearly inFIG. 1B, a cryogenic cooling fluid supply 18, a supply valve 32 andelectrical power source 20 are found within housing 16, along with acircuit 22 having a processor for controlling cooling applied byself-contained system 10 in response to actuation of an input 24.Alternatively, electrical power can be applied through a cord from aremote power source. Power source 20 also supplies power to heaterelement 44 in order to heat the proximal region of probe 26 therebyhelping to prevent unwanted skin damage, and a temperature sensor 48adjacent the proximal region of probe 26 helps monitor probetemperature. Additional details on the heater 44 and temperature sensor48 are described in greater detail below. When actuated, supply valve 32controls the flow of cryogenic cooling fluid from fluid supply 18. Someembodiments may, at least in part, be manually activated, such asthrough the use of a manual supply valve and/or the like, so thatprocessors, electrical power supplies, and the like may not be required.

Extending distally from distal end 14 of housing 16 is atissue-penetrating cryogenic cooling probe 26. Probe 26 is thermallycoupled to a cooling fluid path extending from cooling fluid source 18,with the exemplary probe comprising a tubular body receiving at least aportion of the cooling fluid from the cooling fluid source therein. Theexemplary probe 26 comprises a 27 g needle having a sharpened distal endthat is axially sealed. Probe 26 may have an axial length between distalend 14 of housing 16 and the distal end of the needle of between about0.5 mm and 5 cm, preferably having a length from about 3 mm to about 10mm. Such needles may comprise a stainless steel tube with an innerdiameter of about 0.006 inches and an outer diameter of about 0.012inches, while alternative probes may comprise structures having outerdiameters (or other lateral cross-sectional dimensions) from about 0.006inches to about 0.100 inches. Generally, needle probe 26 will comprise a16 g or smaller size needle, often comprising a 20 g needle or smaller,typically comprising a 25, 26, 27, 28, 29, or 30 g or smaller needle.

In some embodiments, probe 26 may comprise two or more needles arrangedin a linear array, such as those disclosed in previously incorporatedU.S. Pat. No. 7,850,683. Another exemplary embodiment of a probe havingmultiple needle probe configurations allow the cryogenic treatment to beapplied to a larger or more specific treatment area. Other needleconfigurations that facilitate controlling the depth of needlepenetration and insulated needle embodiments are disclosed in commonlyassigned U.S. Patent Publication No. 2008/0200910 entitled “Replaceableand/or Easily Removable Needle Systems for Dermal and TransdermalCryogenic Remodeling,” the entire content of which is incorporatedherein by reference. Multiple needle arrays may also be arrayed inalternative configurations such as a triangular or square array.

Arrays may be designed to treat a particular region of tissue, or toprovide a uniform treatment within a particular region, or both. In someembodiments needle 26 is releasably coupled with body 16 so that it maybe replaced after use with a sharper needle (as indicated by the dottedline) or with a needle having a different configuration. In exemplaryembodiments, the needle may be threaded into the body, it may be pressfit into an aperture in the body or it may have a quick disconnect suchas a detent mechanism for engaging the needle with the body. A quickdisconnect with a check valve is advantageous since it permitsdecoupling of the needle from the body at any time without excessivecoolant discharge. This can be a useful safety feature in the event thatthe device fails in operation (e.g. valve failure), allowing an operatorto disengage the needle and device from a patient's tissue withoutexposing the patient to coolant as the system depressurizes. Thisfeature is also advantageous because it allows an operator to easilyexchange a dull needle with a sharp needle in the middle of a treatment.One of skill in the art will appreciate that other coupling mechanismsmay be used.

Addressing some of the components within housing 16, the exemplarycooling fluid supply 18 comprises a canister, sometimes referred toherein as a cartridge, containing a liquid under pressure, with theliquid preferably having a boiling temperature of less than 37° C. Whenthe fluid is thermally coupled to the tissue-penetrating probe 26, andthe probe is positioned within the patient so that an outer surface ofthe probe is adjacent to a target tissue, the heat from the targettissue evaporates at least a portion of the liquid and the enthalpy ofvaporization cools the target tissue. A supply valve 32 may be disposedalong the cooling fluid flow path between canister 18 and probe 26, oralong the cooling fluid path after the probe so as to limit coolant flowthereby regulating the temperature, treatment time, rate of temperaturechange, or other cooling characteristics. The valve will often bepowered electrically via power source 20, per the direction of processor22, but may at least in part be manually powered. The exemplary powersource 20 comprises a rechargeable or single-use battery. Additionaldetails about valve 32 are disclosed below and further disclosure on thepower source 20 may be found in commonly assigned Int'l Pub. No. WO2010/075438 entitled “Integrated Cryosurgical Probe Package with FluidReservoir and Limited Electrical Power Source,” the entire contents ofwhich is incorporated herein by reference.

The exemplary cooling fluid supply 18 comprises a single-use canister.Advantageously, the canister and cooling fluid therein may be storedand/or used at (or even above) room temperature. The canister may have afrangible seal or may be refillable, with the exemplary canistercontaining liquid nitrous oxide, N₂O. A variety of alternative coolingfluids might also be used, with exemplary cooling fluids includingfluorocarbon refrigerants and/or carbon dioxide. The quantity of coolingfluid contained by canister 18 will typically be sufficient to treat atleast a significant region of a patient, but will often be less thansufficient to treat two or more patients. An exemplary liquid N₂Ocanister might contain, for example, a quantity in a range from about 1gram to about 40 grams of liquid, more preferably from about 1 gram toabout 35 grams of liquid, and even more preferably from about 7 grams toabout 30 grams of liquid.

Processor 22 will typically comprise a programmable electronicmicroprocessor embodying machine readable computer code or programminginstructions for implementing one or more of the treatment methodsdescribed herein. The microprocessor will typically include or becoupled to a memory (such as a non-volatile memory, a flash memory, aread-only memory (“ROM”), a random access memory (“RAM”), or the like)storing the computer code and data to be used thereby, and/or arecording media (including a magnetic recording media such as a harddisk, a floppy disk, or the like; or an optical recording media such asa CD or DVD) may be provided. Suitable interface devices (such asdigital-to-analog or analog-to-digital converters, or the like) andinput/output devices (such as USB or serial I/O ports, wirelesscommunication cards, graphical display cards, and the like) may also beprovided. A wide variety of commercially available or specializedprocessor structures may be used in different embodiments, and suitableprocessors may make use of a wide variety of combinations of hardwareand/or hardware/software combinations. For example, processor 22 may beintegrated on a single processor board and may run a single program ormay make use of a plurality of boards running a number of differentprogram modules in a wide variety of alternative distributed dataprocessing or code architectures.

Referring now to FIG. 2 , the flow of cryogenic cooling fluid from fluidsupply 18 is controlled by a supply valve 32. Supply valve 32 maycomprise an electrically actuated solenoid valve, a motor actuated valveor the like operating in response to control signals from controller 22,and/or may comprise a manual valve. Exemplary supply valves may comprisestructures suitable for on/off valve operation, and may provide ventingof the fluid source and/or the cooling fluid path downstream of thevalve when cooling flow is halted so as to limit residual cryogenicfluid vaporization and cooling. Additionally, the valve may be actuatedby the controller in order to modulate coolant flow to provide highrates of cooling in some instances where it is desirable to promotenecrosis of tissue such as in malignant lesions and the like or slowcooling which promotes ice formation between cells rather than withincells when necrosis is not desired. More complex flow modulating valvestructures might also be used in other embodiments. For example, otherapplicable valve embodiments are disclosed in previously incorporatedU.S. Pub. No. 2008/0200910.

Still referring to FIG. 2 , an optional heater (not illustrated) may beused to heat cooling fluid supply 18 so that heated cooling fluid flowsthrough valve 32 and through a lumen 34 of a cooling fluid supply tube36. Supply tube 36 is, at least in part, disposed within a lumen 38 ofneedle 26, with the supply tube extending distally from a proximal end40 of the needle toward a distal end 42. The exemplary supply tube 36comprises a fused silica tubular structure (not illustrated) having apolymer coating and extending in cantilever into the needle lumen 38.Supply tube 36 may have an inner lumen with an effective inner diameterof less than about 200 μm, the inner diameter often being less thanabout 100 μm, and typically being less than about 40 μm. Exemplaryembodiments of supply tube 36 have inner lumens of between about 15 and50 μm, such as about 30 μm. An outer diameter or size of supply tube 36will typically be less than about 1000 μm, often being less than about800 μm, with exemplary embodiments being between about 60 and 150 μm,such as about 90 μm or 105 μm. The tolerance of the inner lumen diameterof supply tubing 36 will preferably be relatively tight, typically beingabout +/−10 μm or tighter, often being +/−5 μm or tighter, and ideallybeing +/−3 μm or tighter, as the small diameter supply tube may providethe majority of (or even substantially all of) the metering of thecooling fluid flow into needle 26. Previously incorporated U.S. PatentPublication No. 2008/0200910 discloses additional details on the needle26 along with various alternative embodiments and principles ofoperation.

The cooling fluid injected into lumen 38 of needle 26 will typicallycomprise liquid, though some gas may also be injected. At least some ofthe liquid vaporizes within needle 26, and the enthalpy of vaporizationcools the needle and also the surrounding tissue engaged by the needle.An optional heater 44 (illustrated in FIG. 1B) may be used to heat theproximal region of the needle 26 in order to prevent unwanted skindamage in this area, as discussed in greater detail below. Controlling apressure of the gas/liquid mixture within needle 26 substantiallycontrols the temperature within lumen 38, and hence the treatmenttemperature range of the tissue. A relatively simple mechanical pressurerelief valve 46 may be used to control the pressure within the lumen ofthe needle, with the exemplary valve comprising a valve body such as aball bearing, urged against a valve seat by a biasing spring. Anexemplary relief valve is disclosed in U.S. Provisional PatentApplication No. 61/116,050 previously incorporated herein by reference.Thus, the relief valve allows better temperature control in the needle,minimizing transient temperatures. Further details on exhaust volume aredisclosed in previously incorporated U.S. Pat. Pub. No. 2008/0200910.

The heater 44 may be thermally coupled to a thermally responsive element50, which is supplied with power by the controller 22 and thermallycoupled to a proximal portion of the needle 26. The thermally responsiveelement 50 can be a block constructed from a material of high thermalconductivity and low heat capacity, such as aluminum. A firsttemperature sensor 52 (e.g., thermistor, thermocouple) can also bethermally coupled the thermally responsive element 50 andcommunicatively coupled to the controller 22. A second temperaturesensor 53 can also be positioned near the heater 44, for example, suchthat the first temperature sensor 52 and second temperature sensor 44are placed in different positions within the thermally responsiveelement 50. In some embodiments, the second temperature sensor 53 isplaced closer to a tissue contacting surface than the first temperaturesensor is in order to provide comparative data (e.g., temperaturedifferential) between the sensors. The controller 22 can be configuredto receive temperature information of the thermally responsive element50 via the temperature sensor 52 in order to provide the heater 44 withenough power to maintain the thermally responsive element 50 at aparticular temperature.

The controller 22 can be further configured to monitor power draw fromthe heater 44 in order to characterize tissue type, perform devicediagnostics, and/or provide feedback for a tissue treatment algorithm.This can be advantageous over monitoring temperature alone, since powerdraw from the heater 44 can vary greatly while temperature of thethermally responsive element 50 remains relatively stable. For example,during treatment of target tissue, maintaining the thermally responsiveelement 50 at 40° C. during a cooling cycle may take 1.0 W initially andis normally expected to climb to 1.5 W after 20 seconds, due to theneedle 26 drawing in surrounding heat. An indication that the heater isdrawing 2.0 W after 20 seconds to maintain 40° C. can indicate that anaspect of the system 10 is malfunctioning and/or that the needle 26 isincorrectly positioned. Correlations with power draw and correlateddevice and/or tissue conditions can be determined experimentally todetermine acceptable treatment power ranges.

In some embodiments, it may be preferable to limit frozen tissue that isnot at the treatment temperature, i.e., to limit the size of a formedcooling zone within tissue. Such cooling zones may be associated with aparticular physical reaction, such as the formation of an ice-ball, orwith a particular temperature profile or temperature volume gradientrequired to therapeutically affect the tissue therein. To achieve this,metering coolant flow could maintain a large thermal gradient at itsoutside edges. This may be particularly advantageous in applications forcreating an array of connected cooling zones (i.e, fence) in a treatmentzone, as time would be provided for the treatment zone to fully developwithin the fenced in portion of the tissue, while the outer boundariesmaintained a relatively large thermal gradient due to the repeatedapplication and removal of refrigeration power. This could provide amechanism within the body of tissue to thermally regulate the treatmentzone and could provide increased ability to modulate the treatment zoneat a prescribed distance from the surface of the skin. A relatedtreatment algorithm could be predefined, or it could be in response tofeedback from the tissue.

Such feedback could be temperature measurements from the needle 26, orthe temperature of the surface of the skin could be measured. However,in many cases monitoring temperature at the needle 26 is impractical dueto size constraints. To overcome this, operating performance of thesensorless needle 26 can be interpolated by measuring characteristics ofthermally coupled elements, such as the thermally responsive element 50.

One such measured characteristic could be the power required to heat thethermally responsive element 50, therefore the medium which thethermally responsive element 50, or the thermally coupled needle 26, iscoupled to. For example, very little power would be required to warm andmaintain the temperature of the thermally conductive element 50 in air.Various materials could be characterized. For example, the thermallyresponsive element 50 could be used to determine whether the thermallyresponsive element 50, or the thermally coupled needle 26, hassufficient contact with skin due to the thermal load of the skin. Thiswould be useful for ensuring that the needle 26 was correctly placedprior to treatment. This could be done without flowing coolant to theneedle 26, or alternatively, by metering very little coolant to theneedle 26, i.e., less than what is required to treat tissue.

Once the treatment has started, there may be more or less residualrefrigerant that affected the thermally conductive element 50 dependingupon how much thermal load was applied to the needle 26. This could beused to characterize the tissue(s) the probes was placed into. Forexample, there would be relatively more heat drawn from the thermallyconductive element 50 in insulative tissue such as adipose tissue. Sincethermal load on the distal end of the needle 26 would be affected by thedevelopment of an cooling zone around the needle 26, the thermallyconductive element 50 could be used to determine the state of the needle26 as ice forms.

Power feedback could provide feedback to regulate the delivery ofrefrigerant based upon the tissue, formation of ice, contact with theskin, or other useful information. The feedback could be used to controlthe treatment zone to the desired configuration. In addition, thefeedback could be used to diagnose a treatment failure. For instance ifthe probe had three needles delivering refrigerant, but only two wereworking, the thermally conductive element could detect the failure andinform the user.

Temperature feedback could also used in conjunction with power feedback.Temperature sensing could occur on the needle 26 if possible, on thethermally conductive element 50, and/or remote to the thermallyconductive element. For example, the thermally conductive element 50could reside on a detachable cooling probe and be thermally coupled to ahandpiece, with feedback and control circuits located within thehandpiece (e.g., housing 16). This could be advantageous to provide alow cost detachable cooling probe and for system reliability, since theprobe could be coupled to a controller in the reusable handpiece. Thus,practically offering higher capability due to the ability to afford moreprecise controls.

The thermally conductive element 50 could be thermally coupled to theneedle 26 at a proximal tissue interface. When refrigerant wasdelivered, excess refrigerant would return through the needle. Theexcess refrigerant could be in the form of cool gas or liquid that hadnot yet converted to gas through the latent heat of vaporization. Theexcess refrigerant could change dependent upon the tissue(s) the probewas in, variations in tissue temperature, presence of local heat sources(arteries and veins), and metabolic effects. The excess refrigerantcould also be affected by the effect of the treatment over time. Inparticular, changes in thermal loading as a function of the cooling ofadjacent tissue and the formation of ice. The thermally conductiveelement could be tailored to deliver comparable, or more heat than theavailable refrigeration power. However, the transfer of heat into thetissue would be constrained by the material and dimensions of theneedle. For example, a relatively long needle might receive enough heatfrom the adjacent tissue along its length to prevent the freeze zonefrom extending more proximally than desired. Alternatively the abilityto transfer more heat into the tissue could be achieved by providingimproved thermal coupling from the thermally conductive element 50 intothe tissue. This could be achieved by increasing the diameter and orwall thickness of the needle, or through the addition of thermallyconductive cladding to the proximal portion of the needle. This couplingcould also be optimized to extend the length of the protection desired.For instance, the cladding or portion of increased wall thickness anddiameter could extend through the dermis and subdermal fat layer, thenend. Further the cooling of the tip and the heating of more proximaltissue could be uncoupled. This could be achieved by applying aninsulative material between the cladding and the underlying needle.Therefore, the heat through the protected portion of tissue could becontrolled independent of the refrigeration of the tip. This would beadvantageous in that the heat added would not compromise the refrigerantdelivered to the tip and the refrigerant would not comprise the heatadded to the tissue.

Additional methods of monitoring cooling and maintaining an unfrozenportion of the needle include the addition of a heating element and/ormonitoring element into the needle itself. This could consist of a smallthermistor or thermocouple, and a wire that could provide resistiveheat. Other power sources could also be applied such as infrared light,radiofrequency heat, and ultrasound. These systems could also be appliedtogether dependent upon the control of the treatment zone desired.

Alternative methods to inhibit excessively low transient temperatures atthe beginning of a refrigeration cycle might be employed instead of ortogether with the limiting of the exhaust volume. For example, thesupply valve might be cycled on and off, typically by controller 22,with a timing sequence that would limit the cooling fluid flowing sothat only vaporized gas reached the needle lumen (or a sufficientlylimited amount of liquid to avoid excessive dropping of the needle lumentemperature). This cycling might be ended once the exhaust volumepressure was sufficient so that the refrigeration temperature would bewithin desired limits during steady state flow. Analytical models thatmay be used to estimate cooling flows are described in greater detail inpreviously incorporated U.S. Patent Pub. No. 2008/0154,254.

Referring now to FIG. 2 , the flow of cryogenic cooling fluid from fluidsupply 18 is controlled by a supply valve 32. Supply valve 32 maycomprise an electrically actuated solenoid valve, a motor actuated valveor the like operating in response to control signals from controller 22,and/or may comprise a manual valve. Exemplary supply valves may comprisestructures suitable for on/off valve operation, and may provide ventingof the fluid source and/or the cooling fluid path downstream of thevalve when cooling flow is halted so as to limit residual cryogenicfluid vaporization and cooling. Additionally, the valve may be actuatedby the controller in order to modulate coolant flow to provide highrates of cooling in some instances where it is desirable to promotenecrosis of tissue such as in malignant lesions and the like or slowcooling which promotes ice formation between cells rather than withincells when necrosis is not desired. More complex flow modulating valvestructures might also be used in other embodiments. For example, otherapplicable valve embodiments are disclosed in previously incorporatedU.S. Pub. No. 2008/0200910.

Still referring to FIG. 2 , an optional cooling supply heater (notillustrated) may be used to heat cooling fluid supply 18 so that heatedcooling fluid flows through valve 32 and through a lumen 34 of a coolingfluid supply tube 36. In some embodiments safety mechanism can beincluded so that the cooling supply is not overheated. Examples of suchembodiments are disclosed in commonly assigned Int'l. Pub. No. WO2010075438, the entirety of which is incorporated by reference herein.

Supply tube 36 is, at least in part, disposed within a lumen 38 ofneedle 26, with the supply tube extending distally from a proximal end40 of the needle toward a distal end 42. The exemplary supply tube 36comprises a fused silica tubular structure (not illustrated) having apolymer coating and extending in cantilever into the needle lumen 38.Supply tube 36 may have an inner lumen with an effective inner diameterof less than about 200 μm, the inner diameter often being less thanabout 100 μm, and typically being less than about 40 μm. Exemplaryembodiments of supply tube 36 have inner lumens of between about 15 and50 μm, such as about 30 μm. An outer diameter or size of supply tube 36will typically be less than about 1000 μm, often being less than about800 μm, with exemplary embodiments being between about 60 and 150 μm,such as about 90 μm or 105 μm. The tolerance of the inner lumen diameterof supply tubing 36 will preferably be relatively tight, typically beingabout +/−10 μm or tighter, often being +/−5 μm or tighter, and ideallybeing +/−3 μm or tighter, as the small diameter supply tube may providethe majority of (or even substantially all of) the metering of thecooling fluid flow into needle 26. Additional details on various aspectsof needle 26 along with alternative embodiments and principles ofoperation are disclosed in greater detail in U.S. Patent Publication No.2008/0154254 entitled “Dermal and Transdermal Cryogenic MicroprobeSystems and Methods,” the entire contents of which are incorporatedherein by reference. U.S. Patent Pub. No. 2008/0200910, previouslyincorporated herein by reference, also discloses additional details onthe needle 26 along with various alternative embodiments and principlesof operation.

The cooling fluid injected into lumen 38 of needle 26 will typicallycomprise liquid, though some gas may also be injected. At least some ofthe liquid vaporizes within needle 26, and the enthalpy of vaporizationcools the needle and also the surrounding tissue engaged by the needle.An optional heater 44 (illustrated in FIG. 1B) may be used to heat theproximal region of the needle in order to prevent unwanted skin damagein this area, as discussed in greater detail below. Controlling apressure of the gas/liquid mixture within needle 26 substantiallycontrols the temperature within lumen 38, and hence the treatmenttemperature range of the tissue. A relatively simple mechanical pressurerelief valve 46 may be used to control the pressure within the lumen ofthe needle, with the exemplary valve comprising a valve body such as aball bearing, urged against a valve seat by a biasing spring. Thus, therelief valve allows better temperature control in the needle, minimizingtransient temperatures. Further details on exhaust volume are disclosedin U.S. Patent Publication No. 2008/0200910, previously incorporatedherein by reference.

Alternative methods to inhibit excessively low transient temperatures atthe beginning of a refrigeration cycle might be employed instead of ortogether with the limiting of the exhaust volume. For example, thesupply valve might be cycled on and off, typically by controller 22,with a timing sequence that would limit the cooling fluid flowing sothat only vaporized gas reached the needle lumen (or a sufficientlylimited amount of liquid to avoid excessive dropping of the needle lumentemperature). This cycling might be ended once the exhaust volumepressure was sufficient so that the refrigeration temperature would bewithin desired limits during steady state flow. Analytical models thatmay be used to estimate cooling flows are described in greater detail inU.S. Pub. No. 2008/0154254, previously incorporated herein by reference.

In the exemplary embodiment of FIG. 3A, resistive heater element 314 isdisposed near the needle hub 318 and near a proximal region of needleshaft 302. The resistance of the heater element is preferably 1Ω to 1KΩ,and more preferably from 5Ω to 50Ω. Additionally, a temperature sensor312 such as a thermistor or thermocouple is also disposed in the samevicinity. Thus, during a treatment as the needles cool down, the heater314 may be turned on in order to heat the hub 318 and proximal region ofneedle shaft 302, thereby preventing this portion of the device fromcooling down as much as the remainder of the needle shaft 302. Thetemperature sensor 312 may provide feedback to controller 22 and afeedback loop can be used to control the heater 314. The cooling powerof the nitrous oxide will eventually overcome the effects of the heater,therefore the microprocessor may also be programmed with a warning lightand/or an automatic shutoff time to stop the cooling treatment beforeskin damage occurs. An added benefit of using such a heater element isthe fact that the heat helps to moderate the flow of cooling fluid intothe needle shaft 302 helping to provide more uniform coolant mass flowto the needles shaft 302 with more uniform cooling resulting.

The embodiment of FIG. 3A illustrates a heater fixed to the probe hub.In other embodiments, the heater may float, thereby ensuring proper skincontact and proper heat transfer to the skin. Examples of floatingheaters are disclosed in commonly assigned Int'l Pub. No. WO 2010/075448entitled “Skin Protection for Subdermal Cyrogenic Remodelling forCosmetic and Other Treatments”, the entirety of which is incorporated byreference herein.

In this exemplary embodiment, three needles are illustrated. One ofskill in the art will appreciate that a single needle may be used, aswell as two, four, five, six, or more needles may be used. When aplurality of needles are used, they may be arranged in any number ofpatterns. For example, a single linear array may be used, or a twodimensional or three dimensional array may be used. Examples of twodimensional arrays include any number of rows and columns of needles(e.g. a rectangular array, a square array, elliptical, circular,triangular, etc.), and examples of three dimensional arrays includethose where the needle tips are at different distances from the probehub, such as in an inverted pyramid shape.

FIG. 3B illustrates a cross-section of the needle shaft 302 of needleprobe 300. The needle shaft can be conductively coupled (e.g., welded,conductively bonded, press fit) to a conductive heater 314 to enableheat transfer therebetween. The needle shaft 302 is generally a small(e.g., 20-30 gauge) closed tip hollow needle, which can be between about0.2 mm and 5 cm, preferably having a length from about 0.3 cm to about0.6 cm. The conductive heater element 314 can be housed within aconductive block 315 of high thermally conductive material, such asaluminum and include an electrically insulated coating, such as Type IIIanodized coating to electrically insulate it without diminishing itsheat transfer properties. The conductive block 315 can be heated by aresister or other heating element (e.g. cartridge heater, nichrome wire,etc.) bonded thereto with a heat conductive adhesive, such as epoxy. Athermistor can be coupled to the conductive block 315 with heatconductive epoxy allows temperature monitoring. Other temperaturesensors may also be used, such as a thermocouple.

A cladding 320 of conductive material is directly conductively coupledto the proximal portion of the shaft of needle shaft 302, which can bestainless steel. In some embodiments, the cladding 320 is a layer ofgold, or alloys thereof, coated on the exterior of the proximal portionof the needle shaft 302. In some embodiments, the exposed length ofcladding 320 on the proximal portion of the needle is 2 mm. In someembodiments, the cladding 320 be of a thickness such that the cladportion has a diameter ranging from 0.017-0.020 in., and in someembodiments 0.0182 in. Accordingly, the cladding 320 can be conductivelycoupled to the material of the needle 302, which can be less conductive,than the cladding 320.

In some embodiments, the cladding 320 can include sub-coatings (e.g.,nickel) that promote adhesion of an outer coating that would otherwisenot bond well to the needle shaft 302. Other highly conductive materialscan be used as well, such as copper, silver, aluminum, and alloysthereof. In some embodiments, a protective polymer or metal coating cancover the cladding to promote biocompatibility of an otherwisenon-biocompatible but highly conductive cladding material. Such abiocompatible coating however, would be applied to not disruptconductivity between the conductive block 315. In some embodiments, aninsulating layer, such as a ceramic material, is coated over thecladding 320, which remains conductively coupled to the needle shaft302.

In use, the cladding 320 can transfer heat to the proximal portion ofthe needle 302 to prevent directly surrounding tissue from dropping tocryogenic temperatures. Protection can be derived from heating thenon-targeting tissue during a cooling procedure, and in some embodimentsbefore the procedure as well. The mechanism of protection may beproviding latent heat to pressurized cryogenic cooling fluid passingwithin the proximal portion of the needle to affect completevaporization of the fluid. Thus, the non-target tissue in contact withthe proximal portion of the needle shaft 302 does not need to supplylatent heat, as opposed to target tissue in contact with the distalregion of the needle shaft 302. To help further this effect, in someembodiments the cladding 320 is coating within the interior of thedistal portion of the needle, with or without an exterior cladding. Toadditionally help further this effect, in some embodiments, the distalportion of the needle can be thermally isolated from the proximalportion by a junction, such as a ceramic junction. While in some furtherembodiments, the entirety of the proximal portion is constructed from amore conductive material than the distal portion.

In use, it has been determined experimentally that the cladding 320 canhelp limit formation of an cooling zone to the distal portion of theneedle shaft 302, which tends to demarcate at a distal end of thecladding 320. This effect is shown depicted in FIG. 3C where non-targettissue, directly above target tissue, including skin and at least aportion of subcutaneous tissue are not made part of the ice-ball.Rather, cooling zones are formed only about the distal portions of theneedles—in this case to target a temporal nerve branch. Thus, whilenon-target tissue in direct contact with proximal needle shafts remainprotected from effects of cryogenic temperatures. Such effects caninclude discoloration and blistering of the skin.

An exemplary algorithm 400 for controlling the heater element 314, andthus for transferring heat to the cladding 320, is illustrated in FIG. 4. In FIG. 4 , the start of the interrupt service routine (ISR) 402begins with reading the current needle hub temperature 404 using atemperature sensor such as a thermistor or thermocouple disposed nearthe needle hub. The time of the measurement is also recorded. This datais fed back to controller 22 where the slope of a line connecting twopoints is calculated. The first point in the line is defined by thecurrent needle hub temperature and time of its measurement and thesecond point consists of a previous needle hub temperature measurementand its time of measurement. Once the slope of the needle hubtemperature curve has been calculated 406, it is also stored 408 alongwith the time and temperature data. The needle hub temperature slope isthen compared with a slope threshold value 410. If the needle hubtemperature slope is less than the threshold value then a treating flagis activated 412 and the treatment start time is noted and stored 414.If the needle hub slope is greater than or equal to the slope thresholdvalue 410, an optional secondary check 416 may be used to verify thatcooling has not been initiated. In step 416, absolute needle hubtemperature is compared to a temperature threshold. If the hubtemperature is less than the temperature threshold, then the treatingflag is activated 412 and the treatment start time is recorded 414 aspreviously described. As an alternative, the shape of the slope could becompared to a norm, and an error flag could be activated for an out ofnorm condition. Such a condition could indicate the system was notheating or cooling sufficiently. The error flag could trigger anautomatic stop to the treatment with an error indicator light.Identifying the potential error condition and possibly stopping thetreatment, may prevent damage to the proximal tissue in the form of toomuch heat, or too much cooling to the tissue. The algorithm preferablyuses the slope comparison as the trigger to activate the treatment flagbecause it is more sensitive to cooling conditions when the cryogenicdevice is being used rather than simply measuring absolute temperature.For example, a needle probe exposed to a cold environment wouldgradually cool the needle down and this could trigger the heater to turnon even though no cryogenic cooling treatment was being conducted. Theslope more accurately captures rapid decreases in needle temperature asare typically seen during cryogenic treatments.

When the treatment flag is activated 418 the needle heater is enabled420 and heater power may be adjusted based on the elapsed treatment timeand current needle hub temperature 422. Thus, if more heat is required,power is increased and if less heat is required, power is decreased.Whether the treatment flag is activated or not, as an additional safetymechanism, treatment duration may be used to control the heater element424. As mentioned above, eventually, cryogenic cooling of the needlewill overcome the effects of the heater element. In that case, it wouldbe desirable to discontinue the cooling treatment so that the proximalregion of the probe does not become too cold and cause skin damage.Therefore, treatment duration is compared to a duration threshold valuein step 424. If treatment duration exceeds the duration threshold thenthe treatment flag is cleared or deactivated 426 and the needle heateris deactivated 428. If the duration has not exceeded the durationthreshold 424 then the interrupt service routine ends 430. The algorithmthen begins again from the start step 402. This process continues aslong as the cryogenic device is turned on.

Preferred ranges for the slope threshold value may range from about −5°C. per second to about −90° C. per second and more preferably range fromabout −30° C. per second to about −57° C. per second. Preferred rangesfor the temperature threshold value may range from about 15° C. to about0° C., and more preferably may range from about 0° C. to about 10° C.Treatment duration threshold may range from about 15 seconds to about 75seconds and more preferably may range from about 15 seconds to about 60seconds.

It should be appreciated that the specific steps illustrated in FIG. 4provide a particular method of heating a cryogenic probe, according toan embodiment of the present invention. Other sequences of steps mayalso be performed according to alternative embodiments. For example,alternative embodiments of the present invention may perform the stepsoutlined above in a different order. Moreover, the individual stepsillustrated in FIG. 4 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

The heating algorithm may be combined with a method for treating apatient. Referring now to FIG. 5 , a method 100 facilitates treating apatient using a cryogenic cooling system having a reusable or disposablehandpiece either of which that can be self-contained or externallypowered with replaceable needles such as those of FIG. 1B and a limitedcapacity battery or metered electrical supply. Method 100 generallybegins with a determination 110 of the desired tissue therapy andresults, such as the alleviation of specific cosmetic wrinkles of theface, the inhibition of pain from a particular site, the alleviation ofunsightly skin lesions or cosmetic defects from a region of the face, orthe like. Appropriate target tissues for treatment are identified 112(such as the subdermal muscles that induce the wrinkles, a tissue thattransmits the pain signal, or the lesion-inducing infected tissues),allowing a target treatment depth, target treatment temperature profile,or the like to be determined. Step 112 may include performing a tissuecharacterization and/or device diagnostic algorithm, based on power drawof system 10, for example.

The application of the treatment algorithm 114 may include the controlof multiple parameters such as temperature, time, cycling, pulsing, andramp rates for cooling or thawing of treatment areas. In parallel withthe treatment algorithm 114, one or more power monitoring algorithms 115can be implemented. An appropriate needle assembly can then be mounted116 to the handpiece, with the needle assembly optionally having aneedle length, skin surface cooling chamber, needle array, and/or othercomponents suitable for treatment of the target tissues. Simpler systemsmay include only a single needle type, and/or a first needle assemblymounted to the handpiece.

Pressure, heating, cooling, or combinations thereof may be applied 118to the skin surface adjacent the needle insertion site before, during,and/or after insertion 120 and cryogenic cooling 122 of the needle andassociated target tissue. Non-target tissue directly above the targettissue can be protected by directly conducting energy in the form ofheat to the cladding on a proximal portion of the needle shaft duringcooling. Upon completion of the cryogenic cooling cycle the needles willneed additional “thaw” time 123 to thaw from the internally createdcooling zone to allow for safe removal of the probe without physicaldisruption of the target tissues, which may include, but not be limitedto nerves, muscles, blood vessels, or connective tissues. This thaw timecan either be timed with the refrigerant valve shut-off for as short atime as possible, preferably under 15 seconds, more preferably under 5seconds, manually or programmed into the controller to automaticallyshut-off the valve and then pause for a chosen time interval until thereis an audible or visual notification of treatment completion.

Heating of the needle may be used to prevent unwanted skin damage usingthe apparatus and methods previously described. The needle can then beretracted 124 from the target tissue. If the treatment is not complete126 and the needle is not yet dull 128, pressure and/or cooling can beapplied to the next needle insertion location site 118, and theadditional target tissue treated. However, as small gauge needles maydull after being inserted only a few times into the skin, any needlesthat are dulled (or otherwise determined to be sufficiently used towarrant replacement, regardless of whether it is after a singleinsertion, 5 insertions, or the like) during the treatment may bereplaced with a new needle 116 before the next application ofpressure/cooling 118, needle insertion 120, and/or the like. Once thetarget tissues have been completely treated, or once the cooling supplycanister included in the self-contained handpiece is depleted, the usedcanister and/or needles can be disposed of 130. The handpiece mayoptionally be discarded.

As discussed with reference to FIG. 5 , a power monitoring algorithm 115can be applied prior to, during, after, and in some cases in lieu of,the treatment algorithm 114, such as the one shown in FIG. 4 . Oneexample of a power monitoring algorithm 600 is shown in FIG. 6A, whichillustrates a method for monitoring power demand from a heater whencooling fluid is passed through at least one needle. The powermonitoring algorithm 600 can be performed during an actual treatment oftissue. At operation 602, the controller (e.g., controller 22) monitorspower consumption of a heater (e.g., heater 44), which is thermallycoupled to a needle (e.g., needle 26), directly or via a thermallyresponsive element (e.g., element 50). Monitoring can take place duringa tissue treatment procedure, for example, as discussed with referenceto FIG. 5 , performed in parallel to a treatment algorithm.Alternatively, power monitoring can take place during a diagnosticroutine.

At operation 604, the controller correlates a sampled power measurementwith an acceptable power range corresponding to a tissue characteristicand/or operating parameter. This measurement may further be correlatedaccording to the time of measurement and temperature of the thermallyresponsive element 50. For example, during treatment of target tissue,maintaining the thermally responsive element 50 at 40° C. during acooling cycle may be expected to require 1.0 W initially and is expectedto climb to 1.5 W after 20 seconds, due to the needle 26 drawing insurrounding heat. An indication that the heater is drawing 2.0 W after20 seconds to maintain 40° C. can indicate that an aspect of the system10 is malfunctioning and/or that the needle 26 is incorrectly positionedwithin target tissue or primarily positioned in non-target tissue.Correlations with power draw and correlated device and/or tissueconditions can be determined experimentally to determine acceptablepower ranges.

At operation 606, the controller determines whether the powermeasurement is correlated within acceptable limits of an expected powerdraw, or to a power draw indicating a tissue or device problem. Based onthis, a status indication can be provided to the user. If thecorrelation is unacceptable, then the controller may in operation 608initiate an alarm to the user and/or halt or modify the treatmentalgorithm. In some cases, the error is minor, for example, thecontroller may signal a user indication to modify operator technique,e.g., apply greater or lesser pressure to the skin, or that the needleprobe is not fully inserted or that a tissue tent is present. In othercases, the error can indicate a major valve malfunction, and signal analert to abort the process and/or cause a secondary or purge valve tooperate. If the correlation is acceptable, then in operation 610 it isdetermined whether the treatment algorithm is still in process, whichwill cause the power monitoring algorithm to end or continue to loop.Alternatively, the power monitoring algorithm 600 can simply loop untilinterrupted by the controller, for example, when treatment algorithm hasended or by some other trigger.

In some embodiments, the power monitoring algorithm 600 can be performedexclusively for tissue characterization purposes, e.g., to determineproper operating parameters for a later treatment, by only loopingbetween operations 602 and 604 for a predetermined amount of time tocollect data. Data can be collected and correlated by the controller toa particular tissue type and further correlated to optimal treatmentparameters. For example, the characterized tissue may have a greater orlesser average amount of adjacent adipose tissue, which could requirelonger or shorter treatment times. This process could be performed, forexample, by inserting the needle into the target tissue and providingonly enough coolant to characterize the tissue, rather than remodel.

FIGS. 6B and 6C show another power monitoring algorithm 612 forregulating a freeze zone, that can be implemented parallel to or in lieuof a treatment algorithm, such as the one shown in FIG. 4 , as well asparallel to another power monitoring algorithm, such as the one shown inFIG. 6A. At operation 614, a valve 626 is or has been previouslyregulated to provide at least one needle with coolant, with the needlebeing in contact with tissue, as illustrated in FIG. 6C. After sometime, a cooling zone 628 forms within the tissue, and will continue togrow in size as long as the needle is supplied with coolant from coolantsupply 630. Ideally, cooling zone 628 is limited in size to the area oftarget tissue 632, to prevent unintentional treatment of non-targettissue 634. While coolant is flowing, power demand from the heater ismonitored, which can occur immediately or alternatively after apredetermined amount of time has passed since opening of valve 626.

At operation 618, controller 636 determines whether a sampled powermeasurement correlates to a maximum ice-ball size desired for aparticular therapeutic effect, such as tissue remodeling. Correlationswith power draw and cooling zone size can be determined experimentallyto determine acceptable power ranges, and the tissue can bepre-characterized according to a tissue characterization algorithm, suchas shown in FIG. 6A This measurement may further be correlated accordingto the time of measurement and temperature of thermally responsiveelement 638. If the power draw does not correlate with the maximumallowable ice-ball size, then the monitoring is continued.

After a determination that the power demand correlates with the maximumcooling zone size, valve 626 is regulated to provide the needle withless or no coolant at operation 620. After some time cooling zone 628will decrease in size as heat is drawn in from surrounding tissue.During that time, power supplied to the heater is monitored at operation622. At operation 624, controller 636 determines whether a sampled powermeasurement correlates to a minimum ice-ball size required to maintainthe desired therapeutic effect. If the power draw does not correlatewith the maximum allowable ice-ball size, then the monitoring iscontinued while cooling zone 628 continues to decrease in size.

Eventually, at operation 624, the power measurement will correspond withthe minimum cooling zone size. This causes controller 636 to loop theprocess and provide more coolant, which causes cooling zone 628 to growin size. Valve 626 can be metered in this manner to maintain coolingzone 628 within acceptable cooling zone size tolerances (e.g., betweenlower tolerance 640 and upper tolerance 642), until the procedure iscomplete.

The methods disclosed herein involve correlating measured parameters totissue characteristics. An important tissue characteristic is itsability to transfer heat into needle probe(s), or its overall heattransfer rate. The heat transfer rate is a function of the materialproperties of the tissue (e.g., the thermal conductivity (or the thermaldiffusivity which is a function of the thermal conductivity), tissuedensity, and specific heat capacity) as well as the heat transfersurface area.

Confirming that the cryoprobe is fully inserted into the tissue isimportant because it confirms that the cooling zone is in the targettissue. A partially inserted cryoprobe can mean that the cryoprobe iswithin non-target tissue, such as the skin, and thus could cause injuryto such non-target tissues. The controller can monitor the power to theheater and detect conditions when the thermally conductive element onthe proximal end is not in sufficient thermal contact with the skin toprovide protection. This occurs when the skin ‘tents’ around theshoulder of the thermally conductive element along the needle whichlimits to some extent the conductive path between the thermallyconductive element and skin. When insufficient contact is detected thecontroller can terminate treatment to reduce possible tissue injury. Thecontroller may also prevent the start of treatment until adequatecontact is detected between the skin and thermally conductive element.

Steady state heat transfer between the needle probe(s) and the skin canbe described by the following equation q=UAΔT where q is the heattransfer rate, U is the overall heat transfer coefficient, A is the heattransfer area and ΔT is the temperature difference heater block and theskin. The tissue characteristics (including thermal conductivity andthermal diffusivity) are embodied in U and the contacting surface areais also important. It should be noted that this equation describes thesteady state heat transfer, however transient conduction includes thesame parameters and can be characterized in an analogous manner.

To correlate the relative effectiveness of the heat transfer between thecryoprobe and the tissue, the valve can be opened momentarily to allowcooling of tissue. The temperature change of the heater block could thenbe monitored over time. A greater temperature change of the heater blockindicates lower heat transfer between the tissue and the cryoprobe; asmaller temperature change of the heater block indicates a higher heattransfer rate.

Lower heat transfer levels could be correlated with lower thermalconductivity levels or lower thermal diffusivity levels such as occurswhen the needle is inserted in fat. Higher heat transfer rates could becorrelated with higher thermal conductivity or thermal diffusivity suchas occurs when the needles is inserted in muscle. Lower heat transferlevels could also be correlated with less heat transfer surface area.Since the total contacting surface area of the probe is known, heattransfer rates for a fully inserted needle probe(s) can becharacterized. The parameter can be measured when the needle probe isfirst inserted into the patient tissue to determine whether the needleprobe is fully inserted such that the entirety or a predeterminedportion of the needle probe is embedded within tissue.

In some embodiments, the tissue characterization process can includeturning on the heater and opening the valve. Alternately the heater canbe momentarily powered without opening the valve and without cooling.Parameters that can be correlated to tissue characteristics includeheater power, the time rate of temperature change of any of a number oftemperature sensors, or the instantaneous temperature differentialbetween two temperature sensors (e.g., sensors 52/53) as describedbelow.

A temperature T1 of a first location and a temperature T2 of a secondlocation of the probe, e.g, locations of spacially separated sensors52/53 can be measured to estimate the heat flux rate described by theequation q″=(T2−T1)*k/l, where q″ is the heat flux, T2−T1 is thetemperature difference, k is the thermal conductivity of the heaterblock and l is the distance between the two sensors. As disclosed above,higher heat flux rates indicate more heat transfer into the tissue.Alternately, electrical resistance can be measured between the sensorsto confirm that the heater block is in contact with the skin.

A variety of target treatment temperatures, times, and cycles may beapplied to differing target tissues so as to achieve the desiredremodeling. For example, as more fully described in U.S. PatentPublication Nos. 2007/0129714 and 2008/0183164, both previouslyincorporated herein by reference.

There is a window of temperatures where apoptosis can be induced. Anapoptotic effect may be temporary, long-term (lasting at least weeks,months, or years) or even permanent. While necrotic effects may be longterm or even permanent, apoptosis may actually provide more long-lastingcosmetic benefits than necrosis. Apoptosis may exhibit anon-inflammatory cell death. Without inflammation, normal muscularhealing processes may be inhibited. Following many muscular injuries(including many injuries involving necrosis), skeletal muscle satellitecells may be mobilized by inflammation. Without inflammation, suchmobilization may be limited or avoided. Apoptotic cell death may reducemuscle mass and/or may interrupt the collagen and elastin connectivechain. Temperature ranges that generate a mixture of apoptosis andnecrosis may also provide long-lasting or permanent benefits. For thereduction of adipose tissue, a permanent effect may be advantageous.Surprisingly, both apoptosis and necrosis may produce long-term or evenpermanent results in adipose tissues, since fat cells regeneratedifferently than muscle cells.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a number ofmodifications, changes, and adaptations may be implemented and/or willbe obvious to those as skilled in the art. Hence, the scope of thepresent invention is limited solely by the claims as follows.

What is claimed is:
 1. A method for cryogenically treating targettissue, the method comprising: providing a needle probe having at leastone needle with a distal portion and a proximal portion, the needleprobe being coupled to a coolant supply system regulated by a valve,wherein the least one needle is advanced into the target tissue;regulating the valve to provide the at least one needle probe withcoolant to form a cooling zone in the target tissue; providing power toa heater assembly of the needle probe to protect non-target tissue;monitoring at least one characteristic of the heater assembly whileproviding the power to the heater assembly; regulating coolant to theneedle probe using the valve based on a correlation of the at least onemonitored characteristic of the heater assembly and a tissuecharacteristic or an operating parameter.
 2. The method of claim 1,wherein the at least one monitored characteristic comprises temperatureof the heater assembly.
 3. The method of claim 1, wherein the at leastone monitored characteristic comprises the power supplied to the heaterassembly.
 4. The method of claim 1, wherein regulating the coolantsubstantially maintains the cooling zone within an allowable sizetolerance.
 5. The method of claim 4, wherein regulating the coolantcomprises regulating the valve to halt or decrease the coolant flowingin the needle probe long enough for the cooling zone to decrease in sizewithin the allowable size tolerance.
 6. The method of claim 4, whereinregulating the coolant comprises regulating the valve to increase thecoolant flowing in the needle probe long enough for the cooling zone toincrease in size within the allowable size tolerance.
 7. The method ofclaim 4, wherein the allowable size tolerance is determined byperforming a tissue pre-characterization routine using the needle probe.8. The method of claim 1, wherein regulating the valve is based on apredetermined treatment algorithm.
 9. The method of claim 1, wherein theat least one characteristic of the heater assembly comprises at leastone of a heater power, heat transfer rate, heat flux, temperature changerate, or temperature differential.
 10. The method of claim 1, furthercomprising providing a user indication based on the correlation.
 11. Themethod of claim 10, wherein the user indication comprises a tissue type.12. The method of claim 10, wherein the user indication comprises needleprobe status.
 13. The method of claim 10, wherein the user indicationcomprises a malfunction of the valve.
 14. The method of claim 13,further comprising providing a user alert based on the malfunction. 15.The method of claim 1, wherein the operating parameter comprises atleast one of heat transfer rate, heat flux, temperature change rate, ortemperature differential.
 16. The method of claim 1, wherein the tissuecharacteristic comprises a tissue type or depth of insertion of the atleast one needle.
 17. The method of claim 1, wherein regulating thecoolant to the needle probe comprises controlling a treatment time, rateof temperature change, coolant flow rate or temperature.
 18. The methodof claim 1, wherein the at least one needle comprises a needle array.19. The method of claim 1, wherein the at least one needle comprisesthree needles.
 20. The method of claim 19, further comprising providinga user indication that one of the three needles is not working.